I've heard people say that SACD ought to fail in transient reproduction, (because it can only encode a rise and fall relative to the last time step) so I did some calculations:

'Sampling rate' of SACD = 2.8MHz = 64x 44.1kHz

For encoding tones up to 44.1kHz at full scale, it has to reach full-scale from 0 in 64 steps, that is, at any given time there can only be 64 possible positions for the waveform.

This gives it 6 bits resolution to CD's 16 bits??

OK, suppose you only need to encode up to 22.05kHz at full scale, the number of possible positions increases from 64 to 128--7 bits resolution, big improvement

I doubt this is how DSD actually works, but this article http://www.iar-80.com/page40.html (I linked to page 40, but it seems page 1-39 may be going on and on about the sonic flaws of DSD as well) seems to take this view seriously and goes on to talk about how you try to recover musical information from the 6 bit stream.

It is true that human ear cannot hear much above 20 KHz, and this is specially true for dynamic situations. Most people can't hear anything over 19 KHz with steady signals, and maybe over 17-18 KHz on dynamic signals.

This doesn't mean that if you let pass lots of high level ultrasonic garbage (that was not in the original analog signal at all!), due to the lack of a reconstruction filter, there is not going to be problems over the audible range. Most amplifiers have a passband that goes up to 100 KHz. If you let happen that ultrasonic garbage to pass from 22 KHz to 100 KHz, there is a good probability that with such high level ultrasonic signals, the usually greater nonlinearity of the amp at such high frequencies causes intermodulation products that fall into the audible range.

Analog reconstruction filters that filter properly this ultrasonics are very difficult to build, and its properties (stability, phase response, passband ripple) are suboptimal in comparison, that's why they were dropped many years ago. On the other hand, using a simpler low order filter that has good characteristics, it is not possible to filter much of this ultrasonic garbage.

Again, I don't see any problem with today's cd oversampiling digital brickwall filters, in theory. In practice, if some phenomena not taken into account happens, well, show me some proper ABX or double blind tests that prove there is really a problem.

In my opinion, Kusunoki is another of those "illuminate" people who sell expensive esoteric solutions to solve unexisting problems. Same happens with things such as upsampling external DACs, SACD, even things like green pens, cd demagnetizers, cable holders, silver cables, etc.